The main objective of this project is to analyze changes in homotypic cell to cell adhesion during the evolution of chemically induced rat hepatocarcinogenesis, and to identify the cell surface proteins that are involved in this process. The research is currently focused on (1) method developments involving both cell to cell adhesion assays and combination of lecithin based affinity chromatography in combination with two-dimensional gel electrophoresis of cell surface proteins, (2) studies on cell to cell adhesion in normal, preneoplastic and neoplastic hepatocytes, and (3) modulation of transforming growth factors on cell to cell interaction of their target cells. The results so far obtained include: (1) Hepatic cells obtained by perfusing livers with collagenase at different stages of chemically induced (Solt-Farber and/or Peraino method) hepatocarcinogenesis exhibit differential adhesive properties: cells obtained at the preneoplastic nodule stage are more adhesive and cells obtained from a neoplastic stage are less adhesive than normal liver cells. (2) Transforming growth factor beta TGF), when added to the growth medium of normal rat kidney (NRK) cells, elicits a reduction in the ability of the cells to adhere to each other. Epidermal growth factor (EGF) has the apparent capability of reversing the adhesion-impaired effect of TGF. (3) Clones derived from a Fischer rat liver-derived cell line show markedly varying intracellular adhesive characteristics. The differences in adhesiveness roughly correlates with the chromosome number in the cells in each clone, so that cells that have acquired an aneuploid modal chromosome number tend to be more adhesive to each other than cells that have remained diploid during the cloning process. Two-dimensional gel electrophoresis analysis of concanavalin A binding proteins in the cells showed that the cells from the "most adhesive clone" had quantitatively more protein than the "least adhesive" clone; qualitative changes were little. Neither the clones nor the parent cell line, up to passage 34, were able to grow on soft agar in the presence or absence of EGF.